Faculty Profiles - SHIOKAWA, Kazuo

Statistical study of short-period gravity waves in OH and OI nightglow images at two separated sites Reviewed

MK Ejiri, K Shiokawa, T Ogawa, K Igarashi, T Nakamura, T Tsuda

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 108 ( D21 ) 2003.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

[1] Using airglow images of the near-infrared OH band (720 - 910 nm) and OI (557.7 nm) line, we investigated seasonal, latitudinal, and local time variations of short-period gravity waves. The images were obtained at two locations in Japan that are similar to 1200 km apart, Rikubetsu (43.5 degreesN, 143.8 degreesE) and Shigaraki (34.9 degreesN, 136.1 degreesE), between October 1998 and October 1999. Our analysis has focused on small-scale gravity waves with wavelengths less than 40 km and dominant phase speeds of similar to 20 - 50 m/s. Wave occurrences for both OH and OI at Rikubetsu and Shigaraki are significantly higher than 60%, with a slightly larger value in summer. The occurrences increase from evening to midnight. There are no obvious local time dependencies in horizontal wavelength, propagation direction, and phase speed. The propagation directions in summer are either northward or northeastward at both locations. However, in winter the propagation directions at Rikubetsu are generally westward ( NW, W, and SW), whereas those at Shigaraki are only southwestward. From simultaneous wind observation by the MF radars at Wakkanai (45.4 degreesN, 141.7 degreesE) and Yamagawa (31.2 degreesN, 130.6 degreesE), we discuss possible influences of Doppler and thermal ducting, wind filtering, and source distribution of gravity waves propagating from the lower atmosphere to the airglow heights in the mesopause region.

DOI： 10.1029/2002JD002795

Bi-directional electrons in the near-Earth plasma sheet Reviewed Open Access

Shiokawa K, Baumjohann W, Paschmann G

ANNALES GEOPHYSICAE Vol. 21 ( 7 ) page： 1497 - 1507 2003.7

Optical and radio measurements of a 630-nm airglow enhancement over Japan on 9 September 1999 Reviewed Open Access

Otsuka, Y, Kadota, T, Shiokawa, K, Ogawa, T, Kawamura, S, Fukao, S, Zhang, SR

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 108 ( A6 ) 2003.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Blackwell Publishing Ltd

Using a comprehensive data set from optical and radio instruments, we investigate a midnight brightness wave that appeared in 630-nm airglow images over Japan on the night of 9 September 1999. This may be the first such observation of the brightness wave with an all-sky imager in the East-Asian longitudinal sector. The imager at Shigaraki (35.6°N, 136.1°E) tracked a north-northeastward propagation of the wave with an apparent velocity of 500 m s-1 after midnight. Ionosonde observations at five stations in Japan showed that rapid descent of the F2 layer propagated northward beyond 35°N with decreasing amplitude. Incoherent scatter observations with the MU radar at Shigaraki also revealed that the F2 peak altitude decreased from 360 to 280 km during the event. During the F2 layer descent the altitude profile of the electron density became sharp, enhancing the F 2 peak electron density. After the F2 layer altitude reached 280 km, electron density in the F2 layer rapidly decreased because of increased neutral density at low altitude. A Fabry-Perot interferometer (FPI) at Shigaraki observed northward neutral winds of 10-70 m s-1 during the event. A model calculation demonstrates that the meridional winds estimated from the MU radar electron density profiles are fairly consistent with those observed with the FPI. From these results we conclude that the observed northward wind enhancements, probably caused by the midnight temperature maximum, pushed down the plasma in the F2 layer to lower altitudes along the geomagnetic field to cause the 630-nm airglow intensity enhancement. Copyright 2003 by the American Geophysical Union.

DOI： 10.1029/2002JA009594

夜間に観測される海外VHF帯局電波と plasma bubble の相関について Reviewed

P345 オーストラリア・ダーウィンで観測された大気光画像中の重力波の統計解析 Reviewed Open Access

鈴木臣, 塩川和夫, 大塚雄一, 小川忠彦

大会講演予講集 Vol. 83 page： 416 2003.5

長嶋郁生, 中田裕之, 大塚雄一, 鷹野敏明, 坂井来人, 塩川和夫, 小川忠彦

大気電気研究 Vol. 62 page： 91 - 92 2003.4

Ground and satellite observations of nighttime medium-scale traveling ionospheric disturbance at midlatitude Reviewed Open Access

K Shiokawa, Y Otsuka, C Ihara, T Ogawa, FJ Rich

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 108 ( A4 ) 2003.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

[1] We have investigated a nighttime medium-scale traveling ionospheric disturbance (MSTID) observed by an airglow imager at Shigaraki (34.9degreesN, 25.4degreesMLAT), Japan, on 17 May 2001. The structure was identified in the airglow images of OI (630.0 nm and 777.4 nm) as NW-SE band structures (horizontal wavelength: 230 km) moving southwestward with a velocity of 50 m/s. Neutral wind velocity was measured simultaneously from the Doppler shift of the 630.0-nm emission by a Fabry-Perot interferometer at Shigaraki. From these parameters, we performed model calculations of MSTIDs generated by gravity waves and by an oscillating electric field. We found that for the case of gravity waves, the estimated vertical wavelength was too small to explain the observed amplitudes of airglow intensity. For the case of the electric field, we found that an electric field oscillation of similar to1.2 mV/m was sufficient to reproduce the observed airglow amplitudes. This modeled electric field was comparable to that observed by the DMSP F15 satellite as it passed over Shigaraki during our observing period on 17 May 2001. The DMSP ion drift data show that the oscillation of the polarization electric field correlated with the MSTID structure in the airglow image, suggesting that the polarization electric field plays an important role in the generation of MSTIDs.

DOI： 10.1029/2002JA009639

内部磁気圏ミッションの提案

塩川和夫, 関加奈子, 三好由純, 小原隆博, 小野高幸

第3回宇宙科学シンポジウム proceeding page： 435 - 443 2003.4

Statistical study of nighttime medium-scale traveling ionospheric disturbances using midlatitude airglow images Reviewed Open Access

Shiokawa, K, Ihara, C, Otsuka, Y, Ogawa, T

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 108 ( A1 ) 2003.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Blackwell Publishing Ltd

We have investigated statistical characteristics of the nighttime medium-scale Traveling ionospheric disturbances (MSTIDs) observed in 630-nm airglow images at two stations, Rikubetsu (43.5°N, 34.8°MLAT) and Shigaraki (34.9°N, 25.4°MLAT), in Japan for 1998-2000 near the solar maximum period. Most of the observed MSTIDs propagate southwestward in the images. The typical wavelength, velocity, period, and amplitude are 100-300 km, 50-100 m/s, 0.5-1.5 h, and 5-15%, respectively. Seasonal variations in these parameters are not clear. The occurrence rate has a major peak (50-60%) in summer that appears ∼2 months earlier at lower latitudes and a minor peak in winter. Similar occurrence.characteristics are obtained from midlatitude spread-F signatures using multipoint ionosonde data in Japan, though the coincidence of the spread-F and the MSTIDs in airglow images is only 10-15%. Copyright 2003 by the American Geophysical Union.

DOI： 10.1029/2002JA009491

A localized structure in OH airglow images near the mesopause region Reviewed Open Access

Shiokawa K, Ejiri MK, Ogawa T, Yamada Y, Fukunishi H, Igarashi K, Nakamura T

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 108 ( D2 ) 2003.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Atmospheres

An intense localized airglow-depletion structure was observed in OH airglow images (emission altitude ∼86 km) at Shigaraki (34.9°, 136.1°) on 19 December 1998. The structure was a single-band airglow depletion with a small horizontal width (∼15 km) but a large amplitude (∼34% from the average intensity). Airglow rotational temperature indicated a large temperature lapse rate at this time as a result of strong semidiurnal variation. We suggest that nonlinear wave-wave interaction is the most likely cause of this localized structure.

DOI： 10.1029/2002JD002462

A two-channel Fabry-Perot interferometer with thermoelectric-cooled CCD detectors for neutral wind measurement in the upper atmosphere Reviewed Open Access

Shiokawa K, Kadota T, Otsuka Y, Ogawa T, Nakamura T, Fukao S

EARTH PLANETS AND SPACE Vol. 55 ( 5 ) page： 271-275 2003

Seasonal variations of medium-scale gravity wave parameters in the lower thermosphere obtained from spectral airglow temperature imager observations at Shigaraki, Japan Reviewed Open Access

NM Gavrilov, K Shiokawa, T Ogawa

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 107 ( D24 ) page： 7 - 10 2002.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

[1] A method of statistical analysis is used to study parameters of the medium-scale internal gravity waves (IGWs) from the data of the spectral airglow temperature imager (SATI) observations of the OH and O-2 nightglow emissions at Shigaraki, Japan (35degreesN, 136degreesE) during April 1998 to May 2001. Average relative magnitudes of spectral components of airglow variations are 1.8-2.4% for the emission rates and 0.5-1% for the rotational temperature in different seasons. Distributions of periods, horizontal wavelengths, and phase speeds have the main maxima at 0.5-2 hours, 100-500 km, and 50-150 m/s, respectively. In winter, the distributions of propagation azimuths are broad with a dominance in the northwest sector and in the southern half of the sky for OH and in the northwest and southeast sectors for O-2. In spring and summer, IGWs propagate mainly to the northern half of the sky with larger occurrence in the northeast sector for OH emission. Seasonal variations of the average and median IGW magnitudes do not exceed 20-30% and are not stable. In winter, IGWs have maximum occurrence with larger magnitudes, horizontal wavelengths, and phase speeds, particularly at azimuths of 90-210 deg. These results are compared with previous studies.

DOI： 10.1029/2001JD001469

Magnetospheric responses to sudden and quasiperiodic solar wind variations Reviewed Open Access

KH Kim, CA Cattell, DH Lee, K Takahashi, K Yumoto, K Shiokawa, FS Mozer, M Andre

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 107 ( A11 ) 2002.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

[1] On April 13 (day 103), 2001, 0700-1400 UT, the Polar satellite experienced different plasma regimes (i.e., magnetosphere, magnetosheath, and solar wind) because of the solar wind dynamic pressure variations and its high orbital inclination near the subsolar magnetopause meridian. When Polar was in the magnetosheath, quasiperiodic spacecraft potential (SP) variations, corresponding to density variations, with a recurrence time of similar to3-10 min were observed. Using simultaneous solar wind observations, it was confirmed that the magnetosheath SP variations were inherent in the solar wind. We observed an almost one-to-one correspondence between the SP variations and the geomagnetic field perturbations at lower latitudes (L = 1.1-2.8) on the nightside. At higher latitudes (L = 2.9-6.1) on the dayside, however, the field perturbations are more complicated than the magnetosheath SP variations. This suggests that if the magnetospheric perturbations produced by the external source (solar wind/magnetosheath pressure variations) deeply penetrate into the magnetosphere, the lower-latitude data on the nightside are important to monitor the external source variations. In addition, we observed the radial electric field oscillations excited nearly simultaneously with the magnetic field enhancement, associated with a sudden increase in the solar wind dynamic pressure, when Polar was in the magnetosphere. These oscillations may be considered as transient standing Alfven waves excited by externally applied pressure changes as reported by previous studies.

DOI： 10.1029/2002JA009342

New auroral spectrometer using an acousto-optic tunable filter Reviewed

Shiokawa Kazuo, Katoh Yasuo, Satoh Mitsugi, Ogawa Tadahiko, Taguchi Makoto, Yamagishi Hisao

Advances in polar upper atmosphere research Vol. 16 page： 146 - 156 2002.9

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：National Institute of Polar Research

This paper reports the performance and capability of a newly developed zenith spectrometer (for measurements of airglow and aurora) that uses an acousto-optic tunable filter (AOTF). The AOTF can scan the pass-band of the spectrometer between 450 and 700 nm with a bandwidth of 2-3 nm by changing the RF driver frequency from 180 to 100 MHz. The absolute sensitivity of the spectrometer is 〜0.1-1.5 counts/Rayleigh/s per spectral step. The spectrometer is fully automated. The O I (557.7 nm) airglow line can be clearly identified in test observations of midlatitude airglow performed at Shigaraki Observatory, Japan. Based on an estimate of the signal-to-noise ratio, we conclude that the full auroral spectrum (450-700) nm can be measured by the AOTF spectrometer with a time resolution of 〜100 s and a signal-to-noise ratio of 〜100 for an auroral emission intensity of 10 kR. An example of the auroral spectra is shown for observations made at Syowa Station in Antarctica.

CiNii Research

Geomagnetic conjugate observations of equatorial airglow depletions Reviewed

Y Otsuka, K Shiokawa, T Ogawa, P Wilkinson

GEOPHYSICAL RESEARCH LETTERS Vol. 29 ( 15 ) 2002.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

We report for the first time large-scale equatorial F-region airglow depletions extending to low-midlatitudes in both hemispheres. The observational sites were located at low-midlatitude geomagnetic conjugate points. Clear depletions of 630.0-nm airglow intensity due to equatorial plasma bubbles were simultaneously observed with two all-sky imagers at Sata, Japan (magnetic latitude 24degreesN), and its geomagnetic conjugate point, Darwin, Australia (magnetic latitude 22degreesS), on the night of November 12, 2001. Airglow depletion regions with east-west scale sizes of 40-100 km extend poleward. The maximum apex altitude of the plasma bubbles is about 1,700 km over the geomagnetic equator. The depletions move eastward at about 100 m/s, without changing their structures. The Darwin depletion structures mapped onto the northern hemisphere along the geomagnetic field coincide closely with structures in the Sata images, even for the 40-km structure. These observations indicate that plasma depletions in the equatorial ionosphere elongate along the geomagnetic field lines.

DOI： 10.1029/2002GL015347

Multiple auroral brightenings and associated Pi 2 pulsations Reviewed Open Access

K Shiokawa, K Yumoto, JV Olson

GEOPHYSICAL RESEARCH LETTERS Vol. 29 ( 11 ) page： 32 - 1 2002.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

[1] All-sky auroral data at Kotzebue (KOT, 64.4degrees MLAT), Alaska, and magnetic field data from both high- and low-latitude stations are used to demonstrate the relation between multiple auroral brightenings and Pi 2 magnetic pulsations during an isolated substorm. At least five Pi 2 wave packets are identified in the magnetic field data around the end of the growth phase. Auroral luminosity variations do not show oscillations in the Pi 2 frequency range, though each Pi 2 wave packet has good correspondence with each small-scale auroral brightening and poleward motion. This fact may contradict the idea of high- latitude Pi 2 generation by oscillations of substorm field-aligned currents. We discuss possible reasons of this discrepancy from localization of the Pi 2 current system and low-energy electrons as the current carrier.

DOI： 10.1029/2001GL014583

A large-scale traveling ionospheric disturbance during the magnetic storm of 15 September 1999 Reviewed Open Access

K Shiokawa, Y Otsuka, T Ogawa, N Balan, K Igarashi, AJ Ridley, DJ Knipp, A Saito, K Yumoto

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 107 ( A6 ) 2002.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

[1] Using a comprehensive data set and model calculations, we have investigated a prominent large-scale traveling ionospheric disturbance (LSTID) observed in Japan (similar to37degrees-16degrees MLAT) on 15 September 1999, during a recovery phase of sequential storms. The LSTID was detected at 2300-2400 LT (1400-1500 UT) as an enhancement of the 630-nm airglow intensity (50 --> 350 R), a decrease in the F layer virtual height (at 2 MHz, 360 --> 200 km), an enhancement of f(o)F(2) (6 --> 8 MHz), and an enhancement of GPS total electron content (similar to1.0 x 10(16) m(-2)). Multipoint and imaging observations of these parameters show that the LSTID moved equatorward over Japan with a velocity of similar to400-450 m/s. From a comparison with the Sheffield University Plasmasphere-Ionosphere Model (SUPIM) we conclude that an enhancement (250-300 m/s) of poleward neutral wind (that is propagating equatorward) caused these observational features of the LSTID at midlatitudes. To investigate generation of the LSTID by auroral energy input, we have used auroral images obtained by the Polar UVI instrument, magnetic field variations obtained at multipoint ground stations, and the empirical Joule heating rate calculated by the assimilative mapping of ionospheric electrodynamics (AMIE) technique. Intense auroral energy input was observed at 0800-1100 UT (4-6 hours before the LSTID), probably causing equatorward neutral wind at lower latitudes. It is likely that the poleward wind pulse that caused the observed LSTID was generated associated with the cessation of this equatorward wind. The effect of Lorentz force is also discussed.

DOI： 10.1029/2001JA000245

A large-scale traveling ionospheric disturbance during the magnetic storm of 15 September 1999 Reviewed Open Access

Shiokawa K., Otsuka Y., Ogawa T., Balan N., Igarashi K., Ridley A.J., Knipp D.J., Saito A., Yumoto K.

Journal of Geophysical Research Space Physics Vol. 107 ( A6 ) 2002.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research Space Physics

[1] Using a comprehensive data set and model calculations, we have investigated a prominent large-scale traveling ionospheric disturbance (LSTID) observed in Japan (∼37°-16° MLAT) on 15 September 1999, during a recovery phase of sequential storms. The LSTID was detected at 2300-2400 LT (1400-1500 UT) as an enhancement of the 630-nm airglow intensity (50→350 R), a decrease in the F layer virtual height (at 2 MHz, 360→200 km), an enhancement of F<inf>o</inf>F<inf>2</inf> (6→8 MHz), and an enhancement of GPS total electron content (∼1.0 x 10<sup>16</sup> m<sup>-2</sup>). Multipoint and imaging observations of these parameters show that the LSTID moved equatorward over Japan with a velocity of ∼400-450 m/s. From a comparison with the Sheffield University Plasmasphere-Ionosphere Model (SUPIM) we conclude that an enhancement (250-300 m/s) of poleward neutral wind (that is propagating equatorward) caused these observational features of the LSTID at midlatitudes. To investigate generation of the LSTID by auroral energy input, we have used auroral images obtained by the Polar UVI instrument, magnetic field variations obtained at multipoint ground stations, and the empirical Joule heating rate calculated by the assimilative mapping of ionospheric electrodynamics (AMIE) technique. Intense auroral energy input was observed at 0800-1100 UT (4-6 hours before the LSTID), probably causing equatorward neutral wind at lower latitudes. It is likely that the poleward wind pulse that caused the observed LSTID was generated associated with the cessation of this equatorward wind. The effect of Lorentz force is also discussed. Copyright 2002 by the American Geophysical Union.

DOI： 10.1029/2001JA000245